1. Field of the Invention
The present invention relates to a multi-layered printed circuit board (hereinafter, referred to as multi-layered PCB), and more particularly to a multi-layered PCB having an integrated circuit (hereinafter, referred to as IC) embedded (i.e. incorporated) therein.
2. Description of the Related Art
PCBs are used for a wide range of electronic products. Particularly, multi-layered PCBs having a plurality of insulation layers and a plurality of conductive pattern layers stacked alternately are used for laptop computers, portable wireless terminals, and other electronic devices, which require a high level of integration.
FIG. 1 is a sectional view showing a conventional multi-layered PCB, and FIG. 2 is a top view of an IC shown in FIG. 1. The multi-layered PCB 100 has first to fifth insulation layers 111-115 and first to sixth conductive pattern layers 121-126 stacked alternately, as well as an IC 140 embedded therein. The IC 140 is positioned inside the third insulation layer 113, which corresponds to a core insulation layer of the first to fifth insulation layers 111-115. The IC 140 has a plurality of external connection terminals (i.e. bumps) 142 positioned on its surface for electric connection to the exterior.
As the external connection terminals 142 have very small pitch and size, and as the IC 140 needs to undergo a rewiring process, the process during which a plurality of conductive pads 144 are placed in the circuit region of the IC 140, the conductive pads 144 are in one-to-one electric connection with the external connection terminals 142, which are positioned on the periphery of the IC 140, via wires 146. The conductive pads 144, which are larger than the external connection terminals 142, facilitate the electric connection between the IC 140 and the adjacent fifth conductive pattern layer 125.
The multi-layered PCB 100 has a plurality of via-holes 130 for interlayer electric connection so that two adjacent conductive pattern layers are electrically connected to each other through the via-holes. The via holes 130 may be formed by, for example, laser etching.
The electric connection between the IC 140 and the fifth conductive pattern layer 125 is also made through the via-holes 130. Particularly, the fifth conductive pattern layer 125 is electrically connected to the conductive pads 144 through the via-holes 130 positioned between the fifth conductive pattern layer 125 and the IC 140.
However, the conventional multi-layered PCB 100 has several problems. In particular, the electric connection between the IC 140 and the fifth conductive pattern layer 125 requires rewiring of the IC 140, and a plurality of conductive pads 144 need to be placed in the circuit region of the IC 140 during the rewiring process. This degrades the RF characteristics of the IC 140, as a coupling phenomenon occurs between circuit devices formed in the circuit region (e.g. inductors, transistors) and the conductive pads 144 and wires 146.